1. Field of the Invention
This invention relates to an optical information recording and reproducing apparatus for recording and/or reproducing information on optical information recording media. This invention is particularly suitable for an optical card recording and reproducing apparatus which records and reproduces information while relatively reciprocating an optical head and an optical card.
2. Description of the Prior Art
As forms of media for recording and reproducing information using light, there have been known several kinds of media, such as the optical disk, the optical card, the optical tape and the like. Each of these media has different features and is being used according to its proper objects and applications. It is considered, however, that among these media, the optical card will find increasing applications in the future because of its features, such as easiness of production, excellent portability and excellent accessibility.
FIG. 1 is a schematic block diagram exemplifying an optical information recording and reproducing apparatus configured for the above-described card-like optical information recording media. This apparatus is disclosed in U.S. patent application Ser. No. 921,488 (filed Oct. 22, 1986, which issued as U.S. Pat. No. 4,825,059 on Apr. 25, 1989.
In FIG. 1, there are shown an optical card 1 in which information is to be recorded, an optical head 3 (the region surrounded by dotted lines in FIG. 1), a light beam 4, a shuttle 5 for mounting the optical card 1, a laser light source 8 and a collimating lens 9. By a combination of a polarizing beam splitter 10 and a 1/4 wavelength plate 30, a light passing from down to up in FIG. 1 is transmitted, but a light beam passing from above to below is deflected in a perpendicular direction. An objective lens 11 focuses parallel light on the optical card 1.
There are also shown a photosensor 12, a preamplifier 13, an auto-focusing servo 14, an auto-tracking servo 15, a decoder 16, an interface 17, a computer 18, an encoder 19 and a laser driver 20. A stepping motor 21 moves the optical head 3 in the direction perpendicular to the surface of the paper.
A belt 24 is mounted on pulleys 22 and 23. A shuttle 5 for supporting and fixing the optical card 1 is mounted on the belt 24. The pulley 22 is mounted on the shaft of a motor 26, and the optical card 1 reciprocates in the direction of bilateral arrow A in FIG. 1 by the revolution of the motor 26.
Next, the operation of the apparatus shown in FIG. 1 will be explained by illustrating a case of information reproduction.
In FIG. 1, a light beam output by the laser 8 is made a parallel light beam by the collimating lens 9, passes through the polarizing beam splitter 10 and the 1/4 wavelength plate 30, is condensed by the objective lens 11 and forms a minute spot on the optical card 1. The light reflected from the optical card 1 is modulated depending on whether an information pit exists or not in the portion irradiated with the minute spot. The modulated light is again made a parallel light beam by the objective lens 11, and is projected onto the photosensor 12 by the polarizing beam splitter 10. The photosensor 12 detects variations of the amount of light of the modulated light, converts them into electrical signals and sends the signals to the preamplifier 13. The signals are then sent from the preamplifier 13 to the auto-focusing servo 14. By the signals from the auto-focusing servo 14, an actuator (not illustrated) moves the objective lens 11 in the direction of bilateral arrow B, and controls the distance between the objective lens 11 and the optical card 1 so that the light beam 4 focuses on the optical card 1.
The signals from the preamplifier 13 are also sent to the auto-tracking servo 15. By the signals from the autotracking servo 15, an actuator (not illustrated) moves the objective lens 11 in the direction perpendicular to the surface of the paper, and controls so that the light beam 4 focuses on a predetermined position. At the initial operation of the apparatus, servo-draw-in command is sent from the interface 17 to the auto-focusing servo 14 and the auto-tracking servo 15. Some concrete methods have been proposed relative to the auto-focusing servo 14 and the auto-tracking servo 15. In one proposal, for example, the light beam 4 is divided into plural beams by a grating or the like. Tracks for auto-focusing or auto-tracking have previously been preformatted in the optical card 1. Information is reproduced by at least one of the plural light beams, and signals for auto-focusing and auto-tracking are taken out by other light beams. Further, signals from the preamplifier 13 are sent to the decoder 16 and subjected to necessary electrical processing, and subsequently are sent to the interface 17. Information signals are sent from the interface 17 to the computer 18. Signals are also sent from the interface 17 to the encoder 19, and after being modulated whenever necessary, control the oscillation of the laser 8 through the laser driver 20.
Further, signals are sent from the interface 17 to the stepping motor 21 and a motor servo 27, and the position control of the optical head 3 in the direction perpendicular to the surface of the paper and the rotation control of the motor 26 are performed.
In an optical card recording and reproducing apparatus which performs the operation described above, reliability is required such that information can be stably and correctly recorded in optical cards. In order to stably record, an apparatus may be configured so that recorded information pits are reproduced by another spot to confirm whether information has been correctly recorded or not. As such an optical information recording and reproducing apparatus provided with such a spot for monitoring, there is an apparatus shown in U.S. Pat. No. 4,667,316. The disposition of spots in this apparatus is shown in FIG. 2. In FIG. 2, there are shown information tracks 41. On a given information track, a first spot 42 for recording information, and a second spot 45 for reproducing in order to judge immediately after recording whether information recorded as a pit 46 has been recorded correctly or not, are located. Accordingly, even when there is a foreign matter on the information track, it is possible to immediately perform a corrected recording on a new information track 41 on the occasion of a wrong recording, by reproducing the recorded information pit 46 by the second spot 45 and judging whether recording has been correctly performed or not.
However, when the apparatus having a configuration shown in FIG. 2 is applied to an optical card recording and reproducing apparatus in which an optical head and an optical card relatively reciprocate, there is a disadvantage that the recording speed becomes remarkably low. That is, when the roles of the first spot and the second spot are fixed as shown in FIG. 2, recording is necessarily performed during forward movement (or during backward movement, but not both). Consequently, in order to record on two information tracks, the optical head and optical card must accomplish two reciprocating motions. This necessity causes the inconvenience that recording time becomes too long when a large amount of information is recorded.